1. Scope of Invention
This invention relates generally to the use of ferrates of alkali metals for disinfecting contaminated water, and more particularly to a combination of such ferrates contained in dry particle form within a porous packet.
2. Prior Art
The utilization of ferrates as a catalytic agent has been exploited with respect to both novel uses and economy of manufacture. An early U.S. Pat. No. 2,455,696 to Moseman Fischer-Tropsch teaches catalysts that are prepared by reacting Fe(OH).sub.3 with an alkali metal hydroxide and an oxidizing agent to form alkali metal ferrate, after which a mixture of ferrate and powdered iron or iron oxide is heated in the presence of air.
Schreyer, in U.S. Pat. No. 2,536,703 teaches alkali metal ferrates prepared by oxidizing ferrate hydroxide in a strong caustic solution with chlorine gas for use as a deodorizing agent for caustic solutions. In U.S. Pat. No. 2,728,695, Harrison teaches the use of ferrites applied to metallic surfaces for corrosion protection. Mills, in U.S. Pat. No. 2,758,090 teaches the use of orthophosphates and metaphosphates to stabilize ferrates. The unique production of potassium ferrate is also disclosed. In another Harrison U.S. Pat. No. 2,835,553, an alkali metal carbonate is reacted with ferric oxide to yield an alkali metal ferrate (III). From that, an alkali metal ferrate (IV) and then ferrate (VI) are prepared.
BeMiller, in U.S. Pat. No. 3,632,802 teaches the use of alkali metal ferrates to oxidize starch and cellulose. Preparation of ferrates are shown by reacting potassium hydroxide, ferric nitrate and chlorine.
The use of ferrates by Rainer in U.S. Pat. No. 4,246,910 teaches an alkali earth metal ferrate form added to cigarette filters to remove hydrogen cyanide and ammonia. In U.S. Pat. No. 4,304,760, Mein has disclosed potassium ferrate (VI) and a process for removing potassium hydroxide from the crystallized potassium ferrate (VI). Thompson, a co-inventor herein, in U.S. Pat. No. 4,385,045, teaches a method of producing alkali metal ferrates by dry reactions at high temperatures either in a vacuum or in an inert gas atmosphere.
In the Deininger U.S. Pat. No. 4,405,573, the making of potassium ferrate by reacting pure potassium hydroxide, chlorine and a ferric salt in the presence of a ferrate-stabilizing compound is taught. Two additional Deininger U.S. Pat. Nos. 4,435,256 and 4,435,257 also disclose processes for preparing potassium ferrate (VI) by electrochemical methods.
Another of co-applicant Thompson's U.S. Pat. No. 4,535,974 provides further dry technique technology in producing alkali metal ferrates using hematite and magnetite at controlled elevated temperatures. U.S. Pat. No. 4,551,326 also invented by Thompson is a continuation of the previously referenced U.S. Pat. No. 4,385,045.
In two U.S. Pat. Nos. 4,500,499 and 4,606,843, Kaczur teaches the production of highly pure alkali metal or alkaline earth metal ferrates by an extraction process and by vacuum drying a crude ferrate cake of an alkali metal or alkaline earth metal ferrate with at least one alkali metal or alkaline or earth metal hydroxide followed by high temperature drying with heated CO.sub.2 gas.
In another patent to Deininger, U.S. Pat. No. 4,983,306, a process for treating water to remove transuranic elements using an alkali or alkaline earth metal ferrate is there taught. A water soluble salt added to the alkaline earth ferrate is also taught to enhance removal efficiency. Deininger also reviews many prior art processes for the use of ferrate in U.S. Pat. No. 5,202,108 which generally teaches another process for producing ferrate utilizing beta-ferric oxide. Moreover, in U.S. Pat. No. 5,217,584, Deininger further teaches yet another process for producing ferrate employing beta-ferric oxide.
Stable ferrates having the formula MFe,XO.sub.4 in which M is two atoms of either Na or K or one atom of Ca or Ba, X being selected from the group consisting of Al, Si, P, S, CL, Mo, Mn, Cr and mixtures thereof, are prepared by reacting MOH and an oxide with a compound of Fe and X.
Johnson, in U.S. Pat. No. 5,746,994 teaches ferrates which are produced by oxidizing Fe.sup.3+ to FeO.sub.4.sup.2- with monoperoxosulfate in the presence of KOH or NaOH. The availability of ferrates under the trademark TRUCLEAR by Analytical Development Corporation for water purification and waste water treatment are disclosed.
A significant limitation in the use of an alkali metal ferrate in dry or granular form is that, because it is substantially lighter than water, these particles will simply float atop the water to no avail in effecting decontamination thereof. Additionally, after chemically reacting with the water, a non-toxic residue is left in the water in the form of iron oxide particles and other inert impurities which increases the turbidity of the contaminated water and will not decompose thereafter. By the present invention, highly effective alkali metal ferrate (VI) particles, combined with predetermined amounts of an inert insoluble particle material such as clean, dry sand in a uniformly blended mixture with the alkali ferrate (VI) within a porous sealed packet overcome the above limitations in utilizing ferrates (VI) for water decontamination.